Compound of the pyrazolanthrone series



Patented June 13, 1939 UNITED STATES PATENT OFFICE COMPOUND OF THE PYRAZOLANTHRONE, SERIES Earl E. Beard, South Milwaukee, Wis., assignor to E. I. du Pont de Nemours & Company, Wilmington, Del., a corporation of Delaware No Drawing. Application February 24, 1936, Serial No. 65,421

1 Claim.

in the 6 or 7 positions, and dyestuffs obtainable therefrom.

I have found that new and valuable dyestufi intermediates may be produced from l-aminoanthraquinone-fi-aldehyde (and the correspond- 10 ing 7 isomer) by converting the same to the l-hydrazino-anthraquinone-6- (or 7-) aldehyde, which in turn may be ringclosed to the corresponding pyrazolanthrone.

The 1-amino-anthraquinone-6-aldehyde may 5 be prepared by the reduction of l-nitro-anthraquinone-G-aldehyde described by Eckert in Monatshefte fiir Chemie, 1914, p. 289, with alkaline hydrosulfite or sulfhydrate. The diazotization of the l-amino-anthraquinone-6-aldehyde and its reduction to the corresponding hydrazine is carried out by the method usually employed for the preparation of hydrazine compounds of the anthraquinone series from alpha-amino-anthraquinone. The ringclosure of the hydrazine to the 5 pyrazolanthrone is preferably carried out in concentrated sulfuric acid from which the pyrazolanthrone can be separated on dilution from any impurities that may be formed. Other acids, such as glacial acetic acid, may of course be used to effect this ringclosure, in accordance with the process described in the prior art.

In the mononitration of anthraquinone-betaaldehyde there is usually obtained a mixture of l-nitro-anthraquinone-6-aldehyde and l-nitroanthraquinone-7-aldehyde. The l-nitro-anthraquinone-G-aldehyde may be separated from the mixture by means of glacial acetic acid. The 1,? isomer is dissolved in this particular solvent and may be recovered from the glacial acetic acid filtrate. The originally obtained mixture may be reduced to the corresponding amines, diazotized, and converted to the mixed hydrazines, and this material may in turn be subjected to the acid ringclosure. The resulting pyrazolanthrone is,

however, in the main the 1,9-pyrazolanthrone-6- aldehyde since in the reduction process and the subsequent acid conversion to the pyrazolanthrone substantially all of the 7 isomer is eliminated.

The pyrazolanthrone-6-aldehyde may be converted to valuable red dyestuffs by treating with alcoholic alkalies in the manner usually employed in the formation of dlpyrazolanthrone compounds, and then alkylating the dipyrazolanthrones to form the N-dimethyl or N-diethyl dipyrazolanthrone-6,6'-dialdehydes.

The following examples are given to more fully illustrate my invention. The parts used are by weight. 5

Example 1 Ten parts of the 1-hydrazino-anthraquinonefi-aldehyde, prepared by diazotization and reduction of I-NI-IZ-anthraquinQne-G-aldehyde, are dissolved in eighty parts of 93% H2504 and heat ed at -130 C. for from 4 to 5 hours. The mass is then diluted with water and filtered. An excellent yield of 1,9-pyrazolanthrone-6-aldehyde is obtained. It is a dark greenish-yellow powder which dissolves in concentrated sulfuric acid with a yellow color with green fluorescence.

E :tample 2 Example 3 To a suspension of ten parts of the dipyrazolanthrone-6,6'-dialdehyde (prepared according to Example 2) in a mixture of seventy parts nitro- 35 benzene and 8.5 parts sodium carbonate at -1185 C. are added, over a period of from 2 to 3 hours, 8.5 parts of diethyl sulfate, dissolved in twenty parts of nitrobenzene. The temperature is maintained for an additional 4 hours after 40 which the charge is cooled to about 50 C. and filtered. The dyestufi cakeis Washed with nitrobenzene, alcohol and hot water in turns andthen dried. The product obtained dyes cotton in red shades from a greenish blue alkaline hydrosulfite 4.5 vat. It is a red-orange powder which dissolves in concentrated sulfuric acid with an orange color.

Dimethyl sulfate may be used in place of the diethyl sulfate to give the corresponding N-N- 50 dimethyl-dipyrazolanthrone-6,6- dialdehyde.

I claim:

As a new compound, 1,9pyrazolanthrone-6- aldehydee EARL E. BEARD. 55 

